The invention relates to an improved transmission apparatus for high-voltage direct current and, more particularly, to such an apparatus including means for utilizing an inverter operating at a lower voltage than the line voltage of the system to discharge power from the DC line.
In a high voltage DC transmission system, there is typically a rectifier station and an associated inverter station that are connected to a high voltage transmission line having a particular high DC line voltage. In order to discharge energy from the high voltage DC line, it has been necessary to utilize an energy discharge station having an inverter that is dimensioned to operate with the full DC line voltage.
In such prior art systems, such an energy discharge has therefore, only been practical where the power of discharge is of the same order of magnitude as the power associated with the other stations in the system. It has heretofore not been practicable to utilize an inverter for such an energy discharge system having full voltage and lower power.
Accordingly, it is an object of the invention to provide an effective means for operating an energy discharge station for a high voltage DC transmission system with an inverter operating at a direct voltage that is substantially less than the line voltage.
A further object of the invention is to provide a pulse-controlled DC voltage convertor for reducing the line voltage in the discharge station to a level that is reasonable with regard to the desired lower inverter power.
Although DC voltage convertors having pulse-controlled valves and turn-off circuits have been known to the art for low-voltage applications, such convertors have not typically been used for high voltage applications.
Therefore, another object of the invention is to provide a DC voltage convertor that is adapted to operate at high input voltages and to generate a lower output voltage for operation with a lower power discharge thyristor.
A further object of the invention is to provide such a DC voltage convertor that prevents line disturbances from propagating between the DC line and the discharge inverter.
These and other objects of this invention will become apparent from a review of the detailed specification that follows and a consideration of the accompanying drawings in which like reference characters identify identical apparatus.